The present disclosure is related to a projection zoom lens and a projection type display device, for example, to a projection zoom lens that can be favorably used for magnified projection of beams that bear video information from a light valve onto a screen, and to a projection type display device employing such a projection zoom lens.
Conventionally, projection type display devices that magnify and project images displayed on a light valve, such as liquid crystal display elements, are in wide use. In optical systems that utilize transmissive liquid crystal display elements as light valves, cross dichroic prisms are generally employed to combine colors. In order to improve color combining properties taking the angular dependency of the cross dichroic prisms into consideration, it is desired for projection lenses to be employed in such optical systems to be configured to be telecentric at the reduction side. In addition, there is a tendency for zoom lenses which are capable of changing magnification to be preferred as projection lenses, such that image sizes which are projected according to screen sizes can be adjusted even in cases that the degree of freedom of installation conditions is low.
Examples of known zoom lenses which are configured to be telecentric at the reduction side and are suited for use as projection lenses are those disclosed in Japanese Unexamined Patent Publication No. 2008-304765, Japanese Patent No. 5254146, and Japanese Patent No. 5378162. Japanese Unexamined Patent Publication No. 2008-304765, Japanese Patent No. 5254146, and Japanese Patent No. 5378162 disclose zoom lenses constituted by five or six lens groups, in which the lens group most toward the magnification side has a negative refractive power.